Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 17 of 17
Full-Text Articles in Physical Sciences and Mathematics
Ion-Ion Recombination In Mixtures Of Methane And Sulphur Hexafluoride, M. C. Cornell, Ian M. Littlewood
Ion-Ion Recombination In Mixtures Of Methane And Sulphur Hexafluoride, M. C. Cornell, Ian M. Littlewood
Physics Faculty Research & Creative Works
The authors have measured the recombination rate for positive and negative ions in Sulphur hexafluoride and in mixtures of methane and Sulphur hexafluoride in an electron beam sustained discharge. Measurements were made as a function of gas composition, gas pressure in the range 100 to 600 Torr, and reduced electric field strength in the range 12 to 150 Td. When plotted as a function of an effective ion temperature, defined by the drift velocities of the ions in the applied electric field, the rates in each of the gas mixtures follow the same Teff-1.6 power law. From comparisons with theories …
Dynamics Of Multiply Charged Ion-Atom Collisions: U³²⁺+Ne, Ronald E. Olson, J. Ullrich, H. Schmidt-Bocking
Dynamics Of Multiply Charged Ion-Atom Collisions: U³²⁺+Ne, Ronald E. Olson, J. Ullrich, H. Schmidt-Bocking
Physics Faculty Research & Creative Works
Measurements and calculations are presented for the mean recoil-ion energies of Nei+ produced in 1.4 MeV u-1 (0.33 GeV) collisions of U32+ with Ne. Recoil-ion charge states i=1-8 have been observed; the mean recoil energies are low and do not exceed 1 eV until i>6. Calculations employing a newly developed n-body classical trajectory Monte Carlo method are found to yield results in qualitative agreement with the recoil-ion experiment. Calculations also are presented for the ionisation and charge exchange cross sections, the projectile energy loss and the ejected-electron energy and angular spectra. The importance of fast ejected electrons …
Angular-Differential Studies Of Excitation In Quasi-One-Electron Collisions At "High" Energy, E. Redd, Timothy Gay, D. M. Blankenship, John T. Park, Jerry Peacher, Denver G. Seely
Angular-Differential Studies Of Excitation In Quasi-One-Electron Collisions At "High" Energy, E. Redd, Timothy Gay, D. M. Blankenship, John T. Park, Jerry Peacher, Denver G. Seely
Physics Faculty Research & Creative Works
Qualitative differences have been observed between two types of "quasi-one-electron" collision systems. We have studied valence-electron excitation at "high" energy (relative collision velocities up to 0.5 a.u.) in the Mg++He and Na++H collision systems, and find that while Mg++He collisions are dominated by "direct" excitation, the Na++H collisions exhibit significant "molecular" excitation, even at the highest velocities. This behavior can be understood in terms of the molecular structure of the respective collision complexes, and the energy separation between the ground and first excited states of the valence electron.
Site-Diagonal T-Matrix Expansion For Anisotropic Transport And Percolation On Bond-Disordered Lattices, Paul Ernest Parris
Site-Diagonal T-Matrix Expansion For Anisotropic Transport And Percolation On Bond-Disordered Lattices, Paul Ernest Parris
Physics Faculty Research & Creative Works
A study is made of the dynamical behavior of an electron or exciton undergoing anisotropic hopping on a d-dimensional bond-disordered lattice. Starting with a master equation for the site probabilities, an exact equation of motion is obtained for the probability currents that flow along the bonds connecting nearest-neighbor sites. Unlike the original master equation, the equation of motion which couples the microscopic currents contains the randomly distributed hopping rates in a form which is strictly site diagonal. The simplification that results leads to a new and exact expansion for the diffusion tensor in powers of an appropriately defined single-bond t …
Measurement Of The Condensation Coefficient Of Water In The Umr Cloud Simulation Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, A. R. Hopkins, Max B. Trueblood, M. W. Alcorn
Measurement Of The Condensation Coefficient Of Water In The Umr Cloud Simulation Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, A. R. Hopkins, Max B. Trueblood, M. W. Alcorn
Physics Faculty Research & Creative Works
Measurements of the condensation coefficient of water under conditions closely approximating those in natural atmospheric cloud have been made in the cooled-wall UMR cloud simulation chamber. Current measurements disclose a value of condensation coefficient near unity at the outset of the experiment, generally decreasing to lower values (~ .01) as the experiment progresses. The significance of the magnitude of condensation coefficient in atmospheric cloud is briefly discussed.
University Of Missouri--Rolla Cloud Simulation Facility: Proto Ii Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred Raymond Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker
University Of Missouri--Rolla Cloud Simulation Facility: Proto Ii Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred Raymond Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker
Physics Faculty Research & Creative Works
The Graduate Center for Cloud Physics Research at UMR has developed a cloud simulation facility to study phenomena occurring in terrestrial clouds and fogs. The facility consists of a pair of precision cooled-wall expansion chambers along with extensive supporting equipment. The smaller of these chambers, described in this article, is fully operational, and is capable of simulating a broad range of in-cloud thermodynamic conditions. It is currently being used to study water drop growth and evaporation for drops nucleated (activated) on well-characterized aerosol particles. Measurements have been made not only for continuous expansions (simulated updraft) but also for cyclic conditions, …
Separated Resonances In Simultaneous Capture And Excitation Of S¹⁵⁺ In H₂ Observed By K-X-Ray K-X-Ray Coincidences, Michael Schulz, Edson L B Justiniano, Reinhold S. Schuch, Paul H. Mokler, S. Reusch
Separated Resonances In Simultaneous Capture And Excitation Of S¹⁵⁺ In H₂ Observed By K-X-Ray K-X-Ray Coincidences, Michael Schulz, Edson L B Justiniano, Reinhold S. Schuch, Paul H. Mokler, S. Reusch
Physics Faculty Research & Creative Works
We have measured cross sections for the correlated emission of two K x rays following the collision of hydrogenlike sulfur ions with H2 in the energy range between 70 and 160 MeV. The observation of the two correlated x rays is interpreted as a resonant capture of a target electron accompanied by simultaneous excitation of the projectile in the collision (RTE). By our distinguishing between Kα and Kβ lines, contributions from KLL and KLn (n≥M) resonances could be determined independently.
Transport Anisotropy And Percolation In The Two-Dimensional Random-Hopping Model, Kalyan P. Kundu, Paul Ernest Parris, Philip W. Phillips
Transport Anisotropy And Percolation In The Two-Dimensional Random-Hopping Model, Kalyan P. Kundu, Paul Ernest Parris, Philip W. Phillips
Physics Faculty Research & Creative Works
We consider hopping transport on an anisotropic two-dimensional square lattice. The displacements parallel to one axis are governed by uniform, nearest-neighbor hopping rates c, while the displacements parallel to the other axis are governed by static but spatially fluctuating rates wn. Adapting a new class of generating functions recently introduced for the random-trapping problem, we are able to obtain expressions for the mean-square displacement in the fluctuating direction through an exact decoupling of the effects due to displacements in the uniform direction. The resulting expressions for the low-frequency diffusion coefficient D(ε) are exact in the limits c →0 …
Variational Treatment Of A Harmonic Oscillator Coupled To A Dissipative Heat Bath, Paul Ernest Parris, Robert J. Silbey
Variational Treatment Of A Harmonic Oscillator Coupled To A Dissipative Heat Bath, Paul Ernest Parris, Robert J. Silbey
Physics Faculty Research & Creative Works
We consider the problem of a single quantum oscillator coupled linearly to a heat bath of independent harmonic modes. An exact solution is presented for the system-oscillator observables of interest. The exact results are then used to evaluate the utility of a variational approach to the problem that has proven useful recently in elucidating the dynamics of dissipatively coupled systems. We find that the variational approach does provide a good description for most, but not all, observables of interest. Both the exact and the variational treatment demonstrate the important role played by the low-frequency bath modes in determining qualitative features …
Saddle-Point Electrons In Ionizing Ion-Atom Collisions, Ronald E. Olson, Timothy James Gay, H. G. Berry, Edward Boyd Hale, V. D. Irby
Saddle-Point Electrons In Ionizing Ion-Atom Collisions, Ronald E. Olson, Timothy James Gay, H. G. Berry, Edward Boyd Hale, V. D. Irby
Physics Faculty Research & Creative Works
We have studied H++He ionizing collisions, and find that electrons stranded between the two postcollision Coulomb centers dominate the ejected-electron spectra for intermediate (100 keV) projectile energies. The importance of these electrons is clearly established by our classical calculations which are in qualitative agreement, in both shape and magnitude, with experimental spectra taken by us, and with earlier measurements. These saddle-point electrons are produced by a classically understandable mechanism, and are unambiguously observed at nonzero scattering angles. © 1987 The American Physical Society.
Contribution Of Transfer Ionization To Total Electron Capture From A Helium Target, J. A. Tanis, M. W. Clark, R. Price, Ronald E. Olson
Contribution Of Transfer Ionization To Total Electron Capture From A Helium Target, J. A. Tanis, M. W. Clark, R. Price, Ronald E. Olson
Physics Faculty Research & Creative Works
The contribution of transfer ionization (TI) to total electron capture has been measured for Oq+ ions (q=5, 6, 7, and 8) colliding with helium at energies from 0.5 to 1.5 MeV/u. These measurements, along with other published results, suggest a maximum TI contribution to total capture of 0.15q0.5 at E (in keV /u)q0.5100 The results demonstrate that the failure to account for transfer ionization in total single-charge-transfer cross sections may lead to large discrepancies between experiment and theory. © 1987 The American Physical Society.
Oxidation Kinetics Of Polycrystalline Lacro3, Chikung J. Yu, Don M. Sparlin, Harlan U. Anderson
Oxidation Kinetics Of Polycrystalline Lacro3, Chikung J. Yu, Don M. Sparlin, Harlan U. Anderson
Physics Faculty Research & Creative Works
The oxidation kinetics of polycrystalline LaCrO3 were determined by measuring the time and temperature dependence of the weight and conductivity change of reduced samples. A region of fast diffusion followed by a smaller, slower diffusion "tail" was observed in the thermogravimetric measurements. This observation can be interpreted as the rapid diffusion along the grain boundaries and subsequent diffusion into the body of the grain. The absence of the "tail" in the conductivity measurements is due to the high hole mobility along the boundaries. Copyright © 1987, Wiley Blackwell. All rights reserved.
Cw Laser Oscillations And Tuning Characteristics Of Neodymium-Doped Lithium Niobate Crystals, Laird D. Schearer, Michèle Leduc, J. Zachorowski
Cw Laser Oscillations And Tuning Characteristics Of Neodymium-Doped Lithium Niobate Crystals, Laird D. Schearer, Michèle Leduc, J. Zachorowski
Physics Faculty Research & Creative Works
We have obtained over 250 mW of CW laser emission at 1084 nm from a neodymium-doped single crystal of lithium niobate when the rod was end pumped by 1 W from a Kr+ laser at 752 nm, Thresholds of less than 30 mW are obtained with a weak output coupler, rising to 220 mW with a 25 percent transmitting output mirror. The laser could be tuned over 3 nm around the peak at 1084.4 nm with a thirl, uncoated etalon in the cavity. Copyright © 1987 by The Institute of Electrical and Electronics Engineers, Inc.
On A Ferromagnetic With A Three‐Spin Interaction, Harry A. Brown
On A Ferromagnetic With A Three‐Spin Interaction, Harry A. Brown
Physics Faculty Research & Creative Works
No abstract provided.
Test Of Quasiclassical Theories Of Redistribution In Atomic Collisions, Ronald James Bieniek
Test Of Quasiclassical Theories Of Redistribution In Atomic Collisions, Ronald James Bieniek
Physics Faculty Research & Creative Works
The first numerical tests, for a real system, of the Quasi classical description of redistribution of polarized radiation through atomic collisions are presented. Polarization results are reported for red-wing redistribution of Sr (1S0 1P1) in the presence of Ar colliders. They compare favorably to recent quantal, nonadiabatic computations. It is shown that the effects of bent trajectories are important. Modified Quasi classical formulas to account for some of these are presented and tested. The results indicate that Quasi classical analysis can be used to probe the transformation from molecular to atomic states as atoms separate in a half-collision. © 1987 …
Ionization And Charge Exchange In Multiply-Charged-Ion-Helium Collisions At Intermediate Energies, M. L. Mckenzie, Ronald E. Olson
Ionization And Charge Exchange In Multiply-Charged-Ion-Helium Collisions At Intermediate Energies, M. L. Mckenzie, Ronald E. Olson
Physics Faculty Research & Creative Works
A Bohr classical model for He is applied to multiply charged ions colliding with He at intermediate energies. Reactions studied are single-electron capture, single and double ionization, and electron-capture ionization for projectile charge states q=1+ to 100+, and the energy range E=1-5 MeV/amu. The dominant electron-removal collision process is single ionization. For the higher-charge-state ions, single-charge exchange is found to be primarily due to transfer ionization, a two-electron process where one electron is ionized and the other is captured by the projectile. For low-charge states, the single- and double-ionization cross sections are close to the expected q2 and q …
Measurement Of The Condensation Coefficient Of Water In The Umr Simulation Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred R. Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker
Measurement Of The Condensation Coefficient Of Water In The Umr Simulation Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred R. Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker
Physics Faculty Research & Creative Works
The UMR Cloud Simulation Facility is described. The facility is designed to provide a controlled environment simulating the conditions of natural atmospheric processes. It consists of two cooled-wall expansion cloud chambers and peripheral instrumentation for generation and characterization of aerosols used for cloud formation studies. Results of initial studies of the growth of warm cloud droplets and inferred measurements of the condensation coefficient are described.